Small station shear proof punch

ABSTRACT

A shear proof punch with the heels aligned and held in place by a combination of an outer securing ring threaded onto the punch and structure within the outer securing ring that engages the heels and sides of the punch tip to hold them aligned with each other and also limits the outward movement of the heels.

United States Patent [19] Patterson et al.

SMALL STATION SHEAR PROOF PUNCH lnventors: Clinton E. Patterson; Richard J.

Schweiger, both of Minneapolis,

Minn.

Mate Punch and Die Company, Anoka, Minn.

Apr. 13,- 1972 Appl. No.: 243,565

U.S. Cl 83/637, 83/635, 83/686, 83/698, 83/916 Int. Cl B26t 1/14 Field of Search 83/635, 684-689, 83/698, 916

[451 July 3,1973

[56] References Cited UNITED STATES PATENTS 3,296,905 1/1967 Killaly 83/635 X 3,348,443 l0/l967 Smith et al 83/635 X Primary Examiner- J. M. Meister Att0mey'L. A. MacEachron [57] ABSTRACT 3 Claims, 6 Drawing Figures PATENTEU JUL 3 I975 a m mw Illllll SMALL STATION SHEAR PROOF PUNCH BACKGROUND OF THE INVENTION This invention relates to what are known as shear proof punches. They have heels that extend below the surface of the main punch cutting surface. These heels precede the punch tip into the die opening and engage the sides of the opening. In so doing, they prevent lateral movement of the punch which could otherwise occur when a portion only of the punch tip is being used to cut an opening. All of these punches need structure that permits the heels to move easily in response to spring pressure yet assures that they will remain correctly aligned with the main body of the punch. It is also necessary to restrain the heels from excessive axial movement in response to the urging of the springs. On larger punches, there is plenty of room for any structure of this nature that is needed. When these punches are made in very small sizes, say to make an initial cut of one-half inch square, there is very little room for any such securing means. In fact, the only way so far devised prior to this invention was to have vertically extending cap screws or other machine screws. The space requirements for this type of screw structure meant that the punch, while able to be made in fact to out say a V; inch hole, required a shank of a much larger size than the work being done called for. This in turn places limits on which stations of a turret type punch press can be used for these very small punches. It is the contribution of this invention to offer a solution to the problem of making very small shear proof punches that can be used-at the smallest stations of turret type punch presses.

BRIEF DESCRIPTION OF THE INVENTION The heel aligner and restrainer of this invention uses an outer securing ring that threads onto the punch tip to hold the heel aligners and restrainers in place. In one form of the invention the heels aligner and restrainer is a solid ring but in another form it may be segmented. In the latter mentioned form the segmented element may take the form of a collet like member having spring fingers. In any of the segmented forms of the invention, the securing ring may have a slanting inside surface that cooperates with a slanting outer surface on the segmented unit. The securing ring is threaded onto the punch and the two slanting surfaces interact to cause the segments of the segmented unit to move in toward the punch. In the case of the solid ring restrainer, it is simply machined to a nice fit on the punch tip. In both cases, however, the heel aligner provides a nicely fitting member against the side of the punch tip so that no portion of the heel is permitted to extend beyond the side of the punch. These same aligners also engage the heads of the heels to limit how far they can move axially in response to the urging of their springs. Both of these structures will be described in detail in connection with the accompanying drawings which are briefly described below.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged side elevation of the invention with portions broken away to illustrate internal construction clearly, broken lines shown hidden parts;

FIG. 2 is a bottom plan view'of the punch tip and heels drawn to the same scale as FIG. 1; broken lines shown hidden parts and portions of the structure are broken away to show internal structure;

FIG. 3 is a side elevation of the collet form of the invention drawn to the same scale as FIGS. 1 and 2;

FIG. 4 is a bottom plan view of the collet;

FIG. 5 is a fragmentary view like FIG. 1 but of a modified form o f. the invention; and

FIG. 6 is a bottom plan view of the modified form of heel aligner and restrainer.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, the punch body is 10 and is provided with the usual threaded well 11 as a means for screwing the punch to the punch holder of a turret punch press. The lower end of the punch is the punch tip 12 which has vertical grooves in it to receive the heels 14, 15 and 16. A fourth heel, 17 in FIG. 2, does not appear in FIG. 1 because of the cutting away of the punch tip. Springs such as the ones 18 and 19 shown for heels 14 and 16 respectively urge the heels beyond the end of the punch tip 12. All the springs fit into wells in the punch such as the one shown at 22 for spring 18. The spring 18 can be seen to be enough smaller than the head 20 of heel 14 than when the spring 18 is compressed as when the heels 14 engages material to be cut, the head 20 engages a reference surface 24. This reference surface actually supports the heel when it is acting as part of the cutting punch.

The punch tip and heels are embraced by the collet or segmented finger structure 25. Each of the segments or fingers 26, 27, 28 and 29 in FIG. 4 has a pad portion that engages the side of the punch tip 12, at least when they are forced inwardly. Two of these pads, 30 and 31 for the finger 27 and 29 respectively, can be seen in FIG. 3. The inside top of the pads as shown in FIG. 1 provide means for limiting the outward or axial movement of the heels 14-17. The engagement of the inside of the pads 30 and 31 with the heels heads 21 and 20 respectively is seen in FIG. 1

Securing ring 32 encircles the segments of restrainer 25. Segmented unit 25 and securing ring 32 have complementary sloping surfaces that engage each other as seen at 34 in FIG. 1. The female threads of the securing ring 32 mate with the male threads of the punch 10 as seen at 35 in FIG. 1. As the ring 32 is pulled up by the interaction of the threads, the collet 25 bottoms against the surface 24 and further tightening of the securing ring 32 causes the segment fingers to be forced in toward the punch sides as the two sloping surfaces engage each other and interact. As long as the pads of the spring fingers are against the sides of the punch tip, it is not possible for any portion of the heels to extend beyond the side surface of the punch tip 12. Thus the heels are kept aligned.

Singce the segment fingers move a relatively large amount in the collet type structure, it is preferably made from a spring steel and the one found most satisfactory to date is that known as AISI Standar 8-7 In the form of the invention shown in FIGS. 5 and 6,

many of the parts may be identical to those used in the form of the invention illustrated in FIGS. 14. Where this is true, the same number is used to identify the part with the suffix a added to distinguish between the two sets of figures. For example, 18a is a spring in FIG. 5 that is the counter part of and may be identical to the spring 18 in FIGS. 1 and 2.

The main change from the previous shown structure in the alternate form is that the aligning member 40 is a solid wall ring rather than a segmented unit. The opening 42 is machined to close tolerances and fits the punch tip 12 closely enough to align the heads without being tightened. Instead of sloping surfaces that react with each other, therefore, element 40 has the ledge 41 that is engaged by a corresponding ledge 44 on ring 43. This limits the outward movement of the aligning member 40 and so the heels. As shown in FIG. 5, head 20a engages the inside of opening 42 and thus limits the axial movement of heel 14a.

ADVANTAGES Since this punch is used in an obvious and conventional manner, there is really nothing under the heading of operation to be said. There may be some point in discussing how this structure achieves the solution to the problems from which it grew.

As can be seen in FIG. 1 best, the punch does not have to be nearly as large as it would have to be if the heel restaining and aligning members 25 in FIGS. 1-4 and 40 in FIGS. and 6 had to be flanged to receive vertically extending cap screws or the like to hold the restraining structure in place. For this reason, the shear proof punch of this invention can be made to fit the smallest punch receiving station of a turret punch press. Since there are many more small stations than there are ones to receive a large punch, it is very desireable to have as many of the punches that are used fit in the small stations as is possible. In addition, the machining that is necessary to make this structure is all rather basic type of work with nothing extremely difficult to do. Hence the punch can be made relatively easily and yet function in a way that none of the small punches previously made could.

Having thus disclosed our invention we now define the invention in the following claims as required by law.

We claim:

l. A shear proof punch having a punch tip with sliding assymetrical heelsunder a spring load and characterized by:

A. a securing ring encircling said punch tip,

B. cooperating threads on said securing ring and punch tip, and

C. means held within said securing ring that engage the sides of said punch tip and said spring loaded heels to both keep the heels aligned with the sides of said punch tip and to limit their movement as urged by their spring load.

2. The shear proof punch of claim I in which said means held within said securing ring is a segmented means; said securing ring and said segmented means having engaging sloping surfaces; thereby tightening the securing ring forces the segmented means into contact with the punch tip sides.

3. The shear proof punch of claim 1 in which said means held within said securing ring is a ring like member having an opening that nicely fits said punch tip and said securing ring is used to limit axial movement in opposition to the spring load of said spring loaded heels. 

1. A shear proof punch having a punch tip with sliding assymetrical heels under a spring load and characterized by: A. a securing ring encircling said punch tip, B. cooperating threads on said securing ring and punch tip, and C. means held within said securing ring that engage the sides of said punch tip and said spring loaded heels to both keep the heels aligned with the sides of said punch tip and to limit their movement as urged by their spring load.
 2. The shear proof punch of claim 1 in which said means held within said securing ring is a segmented means; said securing ring and said segmented means having engaging sloping surfaces; thereby tightening the securing ring forces the segmented means into contact with the punch tip sides.
 3. The shear proof punch of claim 1 in which said means held within said securing ring is a ring like member having an opening that nicely fits said punch tip and said securing ring is used to limit axial movement in opposition to the spring load of said spring loaded heels. 